1. Technical Field
The present invention relates to a method of manufacturing electro-optical devices in which glass substrates are disposed on external surfaces of a display device.
2. Related Art
In a projection type liquid crystal display device, as one example of an electro-optical device, if dust is adhered on or close to a surface of a liquid crystal panel, the dust is expanded by a projector lens, etc. and is then projected onto a screen, which significantly reduces the display quality. In order to prevent this, for example, as disclosed in Japanese Unexamined Patent Application Publication No. 2003-140125, technologies in which a glass substrate having a dust-proof function is attached to the external surface of the liquid crystal panel have been widely used.
By protecting the external surface of the liquid crystal panel using the glass substrate, dust and the like can be prevented from being adhered on the liquid crystal panel. Further, even if dust, etc. is adhered on the external surface of the glass substrate, the distance between the dust and the liquid crystal becomes wider due to the glass substrate thickness. An image of the dust is thus defocused, and is strongly blurred when displayed on the screen. Therefore, the image of the dust becomes less obvious.
Although the surface of the liquid crystal panel is protected by the glass substrate, it is possible for dust or the like to adhere to a surface of the liquid crystal panel or an inner surface of the glass substrate in the manufacturing process.
The glass substrate is typically adhered to an external surface of a completed liquid crystal panel by means of a heat-curing-type adhesive, and so on. In order to cure the adhesive, a time ranging form about several tens of minutes to one hour is needed. There is, however, a possibility that dust, etc. may enter between the liquid crystal panel and the glass substrate during this process.
Due to this, when the glass substrate is adhered to the liquid crystal panel, it is adhered on one side of the liquid crystal panel by using a heat-curing-type adhesive, and is then fixed by a jig frame in a state in which the glass substrate is positioned at a predetermined location. This prevents dust from entering between the liquid crystal panel and the glass substrate before the heat-curing-type adhesive is cured. Japanese Unexamined Patent Application Publication No. 2004-21056 is an example of related art.
When the glass substrate is adhered, the liquid crystal panel and the glass substrate must be fixed to the jig frame one-by-one. Furthermore, as this has to be individually performed on both sides of the liquid crystal panel, installation and removal of the jig frame become troublesome, and adhesion takes twice as long compared to the curing time of the heat-curing-type adhesive for one liquid crystal panel. Therefore, there is a problem in that the productivity becomes poor.
Moreover, the positioning accuracy of the liquid crystal panel and the glass substrate by the jig frame is about several tens of microns. Thus, there is also a limit to increasing the positioning accuracy.